铈对原代肝细胞内NOS和NO的影响

研究了Ce3+对肝细胞中一氧化氮(NO)和一氧化氮合酶(NOS)的影响.结果表明,Ce3+能使肝细胞中NO含量和NOS活性增加.提示Ce3+有可能影响cGMP信号系统.     

钆铈修饰氧化锌的制备及其可见光催化性能研究

以离子液体1-庚基-3-甲基咪唑溴盐([C7mim]Br)为反应介质,采用水热法制备钆铈修饰纳米ZnO光催化剂。通过SEM、TEM、XRD、UV-Vis等手段对所制备的样品的形貌、物相和结构进行表征。结果表明,以离子液体[C7mim]Br为反应介质制备的ZnO与(Gd3+,Ce4+)-ZnO均属纤锌矿结构;钆铈修饰则有效抑制了ZnO晶粒的生长,使得光响应范围发生红移,且增强了ZnO的可见与紫外光区光吸收。以氙灯为光源,有机染料活性艳蓝为目标降解物,考察纳米ZnO及(Gd3+,Ce4+)-ZnO的光催化活性。光催化活性测试显示(Gd3+,Ce4+)-ZnO对活性艳蓝的去除率(92.36%)远高于ZnO(52.49%),Gd3+、Ce4+共修饰能够显著提高ZnO的可见光活性。     

稀土Ce对钛基Ru-Ce-Ti涂层阳极电催化性能的影响

利用热分解方法在不同温度下制备了不同Ce含量的三元涂层Ru0.3Ti（0.7-x）Ce，O2，通过极化曲线和交流阻抗谱测试，研究了涂层的电催化活性，通过扫描电镜对涂层表面形貌进行了观察。结果表明在涂层中引入Ce可以提高涂层阳极的电催化活性，Ce的掺入量有一个最佳比，摩尔分数为0．2～0．3时电催化性能最好；适宜的热分解温度有利于含Ce涂层阳极性能的提高，最佳温度为450℃。     

Ce离子改性对Cu-SSZ-13催化剂NH3-SCR反应性能的影响研究

Cu-SSZ-13催化剂已被证实是高效NH₃-SCR催化剂。然而,其经过严重水热老化(950℃)后仍会导致不可逆失活。本文通过考察引入的第二活性金属(Ce)离子浓度对Cu-SSZ-13催化剂的活性位性质及其催化活性的影响,揭示了活性位与催化活性之间的关系。结果表明,Cu-SSZ-13中引入的Ce离子并不会成为NH₃-SCR反应的活性中心,而仅起到调节Cu活性位和表面酸性位的位置和数量的作用。通过XPS、H₂-TPR、NH₃-TPD和活性分析结果可知,低铈负载(约0.2%)下,少量的Ce可进入离子交换位点,有助于稳定SSZ-13骨架结构和抑制CuO_x团簇生成的作用(950℃老化后劣化率仅为6%),还能实现高铜负载(Cu负载量为3.01%)与丰富的L酸、B酸位,从而使其具有高的NO转化率、更宽的NO反应温度窗口和优异的水热稳定性。而引入过量的铈离子对Cu-SSZ-13的催化活性和水热稳定性产生不利影响,导致SCR性能下降。     

Ce_xLa_(1-x)活性组分对NH_3-SCR脱硝特性的影响研究

为探究天然氟碳铈矿中Ce和La之间的联合作用对脱硝性能的影响,利用微波加热的方法制备了Ce_xLa_(1-x)活性组分并负载在γ-Al_2O_3上进行了活性测试,其中Ce_(0.8)La_(0.2)催化剂脱硝效果最好,在反应温度为350℃时有78%的NO转化率。BET、NH_3-TPD、XRD、Raman和XPS测试结果表明,Ce_(0.8)La_(0.2)催化剂的活性组分是含有Ce和La的固溶体且具有更好的吸附NH_3能力与更高的比表面积,并且在Ce_(0.8)La_(0.2)催化剂的表面存在的表面吸附氧是提高NH_3-SCR催化性能的原因之一。     

纳米Y_(0.7)Ce_(0.1)Sr_(0.2)M_(1-x)Cu_xO_3(M=Fe,Mn)的制备、表征及其对NO+CO的催化活性

为探究纳米钙钛矿型复合氧化物ABO3中不同B位元素及Cu的掺杂量对催化剂的结构、形貌、表面性质和催化活性的影响规律及原因,并优化出具有更好活性的催化剂,采用柠檬酸-溶胶-凝胶法制备得到8个钙钛矿型复合氧化物Y0.7Ce0.1Sr0.2Fe1-xCuxO3和Y0.7Ce0.1Sr0.2Mn1-xCuxO3(x=0.1~0.4),通过X射线衍射(XRD)、扫描电镜(SEM)、比表面积(BET)、X射线光电子能谱(XPS)等分析方法对其进行了表征,并测试了8个样品对CO+NO的催化活性。结果表明,在Fe、Mn两个系列中,x=0.3时的两个样品对CO+NO分别具有最高的催化活性,Y0.7Ce0.1Sr0.2Fe0.7Cu0.3O3对NO和CO的转化率均在225℃时达到100%,而Y0.7Ce0.1Sr0.2Mn0.7Cu0.3O3对NO和CO的转化率则分别在325℃和225℃时达到100%。Y0.7Ce0.1Sr0.2Fe0.7Cu0.3O3的催化活性优于Y0.7Ce0.1Sr0.2Mn0.7Cu0.3O3,这是由于Fe4+/Fe3+的摩尔比高于Mn4+/Mn3+,并且Y0.7Ce0.1Sr0.2Fe0.7Cu0.3O3中所有Ce4+/Ce3+、Cu+/Cu2+和OA/OL的摩尔比均高于Y0.7Ce0.1Sr0.2Mn0.7Cu0.3O3中相应的摩尔比,而这些因素均有利于NO+CO的催化活性。通过适量的Cu取代B位离子可提高催化剂对NO+CO的氧化还原性,同时Cu的掺杂对于Fe、Mn两个系列中OA/OL的摩尔比具有不同的影响。     

铈改性固体超强酸SO2-4/Sb2O3的制备及催化性能研究

以SbCl3为原料经醇化水解制 Sb2O3前体氧化物,通过浸渍一定量的(NH4)2SO4和掺杂Ce4+制备了一种新型催化剂SO42-/ Sb2O3/Ce4+ .以催化合成乙酸苄酯为探针反应,考察了(NH4)2SO4的浓度、Ce(NO3)4 的浓度、焙烧温度等因素对其催化性能的影响,并采用IR、TG/DTA、Hammett法等对其进行表征.结果表明,1.5 mol·L-1的(NH4)2SO4和含Ce(NO3)4 2.8%的混合液浸渍锑前体氧化物,经110℃烘干后,于350℃焙烧2 h所得的催化剂活性最好,其酯化率达到97%..     

铈钨比对CeO_2-WO_3/TiO_2蜂窝催化剂的脱硝活性影响研究

采用挤出成型法制备了一系列不同Ce/W摩尔比的CeO_2-WO_3/TiO_2蜂窝催化剂,并评价了其SCR脱硝活性。结果发现,当Ce/W摩尔比为4∶1时,催化剂的低温活性最好。采用XRD、SEM、BET、H_2-TPR及NH_3-TPD对催化剂的物化性质进行表征。当Ce/W摩尔比为4∶1时,催化剂的X射线衍射曲线中CeO_2(111)晶面衍射峰最强,EDS测得的Ce含量最高。SEM检测结果显示,此时催化剂表面的孔道结构最丰富,催化剂的比表面积也达到最大值。此外,H_2-TPR和NH_3-TPD的测试结果分别表明,该催化剂的表面分布有最多的表面氧,且存在较多的酸性位,使其表现出良好的低温脱硝活性。     

纳米Ce/TiO2光催化剂的制备及光催化性能

以TiCl4为原料,Ce(NO3)2·6H2O为掺杂剂,制备了铈掺杂TiO2纳米粒子并进行了X射线衍射表征和气相光催化性能评价。实验结果表明,铈掺杂对样品的光催化活性有影响,随着掺铈量的增加样品的光催化活性提高。掺铈量大于4%以后活性变化不再明显。样品的焙烧温度和时间也对样品的光催化活性有影响。此外,样品的粒径随制备中的pH值降低而减小。     

Ce4+对悬浮培养南方红豆杉细胞DNA含量和PAL活性的影响

本文动态观察了不同浓度 Ce4 作用下悬浮培养体系中南方红豆杉细胞核 DNA含量、细胞活力、苯丙氨酸转氨酶 (PAL )活性及紫杉醇含量的变化规律 ,并比较了不同浓度 Ce4 对这些指标影响的差异。结果表明 :在悬浮培养体系中加入适当浓度 Ce4 ,在其作用早期对南方红豆杉细胞的增殖能力、细胞活力及紫杉醇含量均有明显的促进作用 ;Ce4 对细胞的生物效应中浓度是一重要因素 ,同时细胞自身所处的生理状态也影响稀土离子作用的结果     

Effects of Lanthanum and Cerium on Acid Phosphatase Activities in Two Soils

To evaluate the security of using thulium, comparision between effects of La and those of Ce on acidic phosphatase activities in red soil and yellow soil in Zhejiang district was studied under conditions of ambient temperature and humidity. Results show that the acid phosphatase from different soil respondes to La and Ce differently. The activity of acid phosphatase in soil 1 declines with the increase of the concentration of La and Ce. The maximum inhibitory ratio of La and Ce reaches 69.8% and 71.0% respectively. But La and Ce have stimulative effect on the activity of acid phosphatase in soil 2.Under the effect of same concentration of the thulium, the acid phosphatase in two soils increases with the extending of culture time.     

Calcium additional to that bound to the transport sites is required for full activation of the sarcoplasmic reticulum Ca-ATPase from skeletal muscle

The sarcoplasmic reticulum Ca-ATPase is fully activated when approximately 1 microM [Ca2+] saturates the two transport sites; higher [Ca] inhibits the ATPase by competition of Ca-ATP with Mg-ATP as substrates. Here we describe a novel effect of EGTA and other chelators, raising the possibility of an additional activating effect of Ca in the sub- or low microM range. Sarcoplasmic reticulum membranes were isolated from rabbit skeletal muscles. The ATPase activity was measured after incubation at 37 degreesC in 3 mM ATP, 3 mM MgCl2, 50 mM MOPS-Tris (pH 7.2), 100 mM KCl, and variable CaCl2, EGTA and calcimycin. In the absence of added EGTA and Ca the ATPase activity is high due to contaminant Ca. The determination of the ATPase activity in the presence of increasing amounts of EGTA, without added Ca, yields a decreasing sigmoidal function. Ki ranged between 20 and 100 microM, depending on the enzyme concentration. Pi production is linear with time for several [EGTA] yielding suboptimal ATPase activities, which are inhibited by thapsigargin. These suboptimal Ca-ATPase activities are inhibited by preincubation of the enzyme in EGTA, at pH 7.2. This effect increases upon increasing EGTA concentration and preincubation time. The inhibitory effect of the previous exposure of the enzyme to EGTA is partially but significantly reverted by increasing [Ca2+] during incubations. Calcimycin and EDTA have similar effects as EGTA when added in preincubations. The effect of calcimycin is fully reverted by optimal [Ca2+] in incubations. The effects of EGTA, EDTA and calcimycin in preincubation are not additive. The results suggest that an additional calcium, lost during preincubations from a site with affinity near 1 microM, is necessary for full activation of the ATPase.     

Intracellular distribution of the Wilson's disease gene product (ATPase7B) after in vitro and in vivo exogenous expression in hepatocytes from the LEC rat, an animal model of Wilson's disease

In patients with Wilson's disease, both copper incorporation into ceruloplasmin and excretion of this metal into bile are impaired. These conditions are caused by a genetic defect in the Wilson's disease gene (ATP7B). To investigate the Wilson's disease gene protein (ATPase7B) in hepatocytes, we constructed an expression plasmid carrying full-length complementary DNA for human Wilson's disease gene and attempted to express the gene in hepatocytes of LEC rats, an animal model of Wilson's disease. Transfection of hepatocytes, either in vitro or in vivo, was done using a newly developed cationic liposome containing 1,4-bis(3-(N-hexadecyl) aminopropyl) piperazine. Immunological analyses of human ATPase7B with specific monoclonal antibodies showed human ATPase7B to be a membrane protein with a molecular mass of 155 kd. Analysis of human ATPase7B expressed in hepatocytes from LEC rats suggested that this protein is present in the trans-Golgi network and at the plasma membrane, a distribution pattern similar to that of Menkes' disease protein (ATPase7A). These findings suggest that these two putative copper-transporting P-type ATPases function similarly at the cellular level. Cotransfection and coexpression of the human Wilson's disease gene and ceruloplasmin gene in cultured hepatocytes indicate that the distribution of ceruloplasmin is always accompanied by ATPase7B at the perinuclear region, but that part of ATPase7B localizes irrespective of the distribution of ceruloplasmin. Based on these investigations, we propose that ATPase7B exists in the trans-Golgi network and transports copper into this compartment. This seems to ensure an appropriate delivery of copper to the apoceruloplasmin. On the other hand, part of ATPase7B that is not accompanied by ceruloplasmin in the perinuclear region and at the plasma membrane seems to contribute to efflux of this metal from the hepatocytes. Thus the distribution patterns of ATPase7B in hepatocytes may explain the dual roles of this P-type ATPase in hepatocytes.     

Toxic Effects of Lanthanum, Cerium, Chromium and Zinc on Potamogeton Malaianus

iththerapiddevelopmentofrareearthindustryandextensiveapplicationofrareearthinagriculture ,agreatmanyofrareearthelements (REEs)werere leasedintoenvironment ,especiallywaterenviron ment ,andtheconsequentseriousenvironmentpollu tionhasattractedpeople′satten…     

Effect of fluxes on structure and luminescence properties of Y3Al5O12：Ce^3＋ phosphors

Ce3+-activated yttrium aluminum garnet (YAG) was prepared by the solid-state reaction, in which H3BO3, LiF, NaF, KF and BaF2 were used as the fluxes. The effect of fluxes on optical properties of phosphors was studied in detail, especially the fluxes of alkali fluorides, which could enhance the emission intensity and change the wavelength of emission peaks. Among these YAG:Ce phosphors, the phosphor sintered with H3BO3 and NaF exhibited the strongest emission. The emission peaks of phosphors prepared with fluxes from LiF to KF were shifted to long wavelength. The effect of NaF concentration on the emission intensity of YAG:Ce was also investigated. The value of emis-sion intensity reached the maximum when the concentration of NaF was 0.5%.     

The trivalent cerium-induced cell death and alteration of ion flux in sweetpotato [Ipomoea batatas(L.) Lam]

The rare earth element cerium(Ce) in its several forms is extensively utilized in various fields, including nano-technology, agriculture, and the food industry. Due to its increasing unregulated usage, Ce is now a potential source of pollution and toxicity due to its excessive environmental accumulation. Unfortunately, analysis of the toxic effects of Ce in plants is still in its early stages. Herein, we investigated the effects of Ce3+ treatment on development-related indicators in sweetpotato. We found that a low concentration(10 mg/L) slightly improved oxidation resistance, while a high concentration(20-80 mg/L)negatively affected development and photosynthesis and triggered increases in reactive oxygen species(ROS) production, antioxidant enzyme activities, and malondialdehyde(MDA) content. Moreover,elevation and efflux of cytosolic Ca~(2+) and caspase-l-like activity were induced by high-concentration Ce~(3+) treatment. Finally, cell viability decreased as Ce3+ concentration increased. These results suggest that(1) a high Ce3+ concentration(20-80 mg/L) inhibits development and photosynthesis of sweetpotato and induces oxidative damage followed by lipid peroxidation in the root,(2) a caspase-l-like protease is induced by cytosolic Ca~(2+) and ROS overproduction to cause programmed cell death in the root, and(3) a high concentration of Ce3+ could trigger a hypothetical cell death pathway, wherein Ce3+induces ROS production followed by cytosolic Ca~(2+) elevation, which activates caspase-l-like activity,which in turn leads to programmed cell death in the root of sweetpotato.     

Effect of Ce3＋ on membrane permeability ofEscherichia coli cell

This study aimed to delineate the antibacterial mechanism of rare-earth ion Ce 3+ to the target organism Escherichia coli cell, and the most important purpose was to identify its biological effect of increasing the E. coli cell membrane permeability. The antibacterial activities of Ce 3+ to E. coli cells were tested, and then the permeability of outer membrane (OM) and inner membrane (IM) were studied by N-phenyl-1-naphthylamine (NPN) and o-nitrophenyl-β-D-galactopyranoside (ONPG) methods separately. Through these experiments we concluded that the E. coli cells grown to log phage were more sensitive to Ce 3+ than the ones not at this stage; the structure of membrane was destroyed and the permeability of both OM and IM was obviously increased by Ce 3+ ; there should be certain interactions between Ce 3+ and some proteins inside the cell, which impeded the physiological activities of bacteria.     

Vanadate-sensitive microsomal ATPases and microsomal 45Ca2+ uptake in tracheal epithelial cells

Cytosolic free Ca2+ plays important roles in the regulation of physiological processes in tracheal epithelial cells and is probably regulated by many ion-transporting ATPases in these cells. Therefore, the effect of vanadate was investigated to characterize microsomal ion-transporting ATPases. Dose response experiments showed that vanadate had a biphasic effect on the microsomal ATPase activity: a decrease at the vanadate concentration below 100 microM, and a steep decrease at the concentration above 100 microM. The dose response data were fitted to two sigmoidal functions, corresponding to a low-affinity vanadate-sensitive (LAVS) ATPase and a high-affinity vanadate-sensitive (HAVS) ATPase. In 45Ca2+ uptake experiments, both LAVS and HAVS ATPases mediated microsomal 45Ca2+ uptake. The LAVS ATPase was selectively sensitive to thapsigargin in both ATPase activity and 45Ca2+ uptake, suggesting that it is an ER/SR-type intracellular Ca2+-ATPase. Although the HAVS ATPase mediated one-fourth of microsomal 45Ca2+ uptake, its activity was not sensitive to thapsigargin. These results indicate that the activities of these two vanadate-sensitive ATPases are mediated by different enzymes, since thapsigargin only blocks the activity of LAVS ATPase. In conclusion, there are two types of vanadate-sensitive microsomal ATPases, and these ATPases mediate microsomal 45Ca2+ uptake in airway epithelial cells.     

Photocatalytic activity of cerium-doped mesoporous TiO2 coated Fe3O4 magnetic composite under UV and visible light

A novel kind of magnetically separable photocatalyst of cerrium-doped mesoporous titanium dioxide coated magnetite (Ce/MTiO2/ Fe3O4) was prepared and its activities under UV and visible light were reported. The catalysts with Ce/MTiO2 shell and Fe3O4 core were pre-pared by coating photoactive Ce/MTiO2 onto a magnetic Fe3O4 core through the hydrolysis of tetrabutyltitanate (Ti(OBu)4, TBT) with pre-cursors of ammonium ceric nitrate and TBT in the presence of Fe3O4 particles. The MTiO2 shell was for photocatalysis, the Fe3O4 core was for separation by the magnetic field and the doped Ce was used to enhance the photocatalytic activity of MTiO2. The morphological, struc-tural and optical properties of the prepared samples were characterized by Brunauer-Emmett-Teller (BET) surface area, transmission electron microscopy (TEM), X-ray diffraction (XRD) and UV-vis absorption spectroscopy. The effect of cerrium-doped content on the photocatalytic activity was studied and the result revealed that 0.5 mol.% Ce/MTiO2/Fe3O4 exhibited highest photoactivity. The photocatalytic activities of obtained photocatalysts under UV and visible light were estimated by measuring the degradation rate of methylene blue (MB, 50 mg/L) in an aqueous solution. The results showed that the prepared photocatalyst was activated by visible light and used as effective catalyst in photooxi-dation reactions. In addition, the possibility of cyclic usage of the prepared photocatalyst was also confirmed. Moreover, Ce/MTiO2 was tightly bound to Fe3O4 and could be easily recovered from the medium by an external magnetic filed. So, the photocatalyst can be reused without any mass loss. It can therefore be potentially applied for the treatment of water contaminated by organic pollutants.